I think people have a tendency to place on "checks and balances" things it wasn't meant to. The Federalist papers talk about the distribution of legislative, judicial, and executive power. It isnt checks and balances over garden variety criminality.
IMO this would be an example of the Executive branch having, in effect, no check on its power because the Legislative are asleep at the wheel (due to partisanship) and the Judicial have been carefully picked to ensure that any issues blocked by lower courts over which the Executive have less power can be reversed by SCOTUS.
In any case, if Russian collusion is demonstrated, it's not common or garden variety criminality IMO.